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Scitech

Test Mystery Powder

Tasty or toxic? Things can look similar but be completely different. Learn how to tell white powders apart with simple chemistry.

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What you’ll do

Often things can look the same but be very different. If you have two white powders, how would you tell which one is tasty and which one is toxic?

In this experiment, you’ll use red cabbage solution to test mystery powders. Learn how to make an indicator, so you can characterise mystery substances, with no risk to your tastebuds.

 

What you’ll need

  • 5 white powders – these are your known substances (e.g. sherbet, washing powder, cornflour, cream of tartar and baking powder)
  • 6 small containers (these could be small clear bowls or clear plastic shot glasses)
  • 1/2 red cabbage
  • Water
  • Kettle
  • Large heat safe bowl
  • Sieve
  • Jug or other container for cabbage juice
  • Eyedropper or teaspoon
  • Glass or cup
  • Pen and paper
  • Marker pen

 

Instruction

Prepare the evidence

Before conducting this experiment, ask an adult to:

  1. Select one of the five white powders to use as a mystery white powder or “evidence” from a crime scene.
  2. Place a small amount (1 teaspoon) of this white powder into a bowl.
  3. Using a marker, label the bowl ‘E’ for evidence.

Note: The next step requires active adult involvement to make red cabbage solution.

Prepare the red cabbage solution

  1. Boil a kettle of water.
  2. Chop the red cabbage into pieces.
  3. Place the red cabbage pieces into a large heat safe bowl.
  4. Add the boiling water to the red cabbage so all the cabbage is covered by water.
  5. Leave the cabbage and hot water to stand for about 10 minutes.
  6. Place a kitchen sieve over the storage container (jug or jar).
  7. Pour the cabbage mixture through the sieve into the storage container.
  8. Discard the cabbage leaves.
  9. Put a lid or cover on the jug or jar and leave at room temperature.
  10. This is your red cabbage solution.

Mystery powder analysis:

  1. Place a small amount (1 teaspoon) of each white powder into individual small bowls.
  2. Label each of the five bowls with the name of powder it contains.
  3. These are samples of your known substances.
  4. Take the pre-prepared evidence sample, in the bowl labelled ‘E’.
  5. Fill a small glass halfway with the red cabbage solution.
  6. Using an eye dropper or teaspoon, add 1ml of red cabbage solution to the evidence sample.
  7. Record the colour change.
  8. Next, add 1ml of red cabbage solution to each of the five known substances.
  9. Record the colour change of each of these substances.
  10. Compare the resulting colours to determine which known substance most closely matches the mystery powder.
  11. You can now identify your mystery white powder.

 

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